Stencil



Oct. 6, 1936. A M GOMES 2,056,427

STENCIL Filed- Feb'. 28, 1933 INVENTOR 44.55970 M Q0/1455.

Patented Oct. 6 1936 UNITED STATES PATENT orrlca This invention relatesto new and useful improvements in stencils and more particularly itpertains to stencils of the type employed in cornneetion withduplicating machines, sills screen stencil frames and similarduplicating apparatus.

The stencil forming the subject of thisinvention is intended in itsultimate form to be of the sensitized type and although I am aware thatsensitized stencils have been heretofore manufactured, all such stencilswith which I am familiar have many disadvantages.

' sensitized stencils with which I am familiar are completed in theirsensitized form at the time of their manufacture. Such stencils aresubject to rapid deterioration as a result of atmospheric, temperatureand other conditions and under certain conditions are unfit for use amonth after their manufacture. Also, such stencils are de veloped afterexposure, by means of heated solu= tions which invariably causesexpansion of the stencil which isfollowed by contraction as thefinishing steps are carried out. These inherent conditions render suchstencils practically useless for the productionof multi-colored worksince to produce such work a number of stencils must be employed andinasmuchas they cannot be .uniformly manufactured perfect registrationcannot be obtained. Furthermore, the several solutions with which thesestencils are treated have a tendency to render the stencils more or lessrigid and unpliable, thus rendering them liable to damage in use.

A feature of the invention resides in a novel method of manufacturingsensitized stencils which method permits of the ultimate user performingfor himself the sensitizing step of the method or process.

' Another feature of the invention resides in a novel method wherebystencils which are of uniform character may be produced. This feature isparticularly important for the reason that uniform stencils permit ofobtaining perfect registration therefore making possible the attainmentof perfect results with said stencils in multicolor work.

A further feature of the invention resides in the provision of asensitized stencil in which it is not necessary to protect the stencilfrom the action of light except over extended periods. Such a stencilmay be prepared and handled in lights of ordinary intensity without dev2w. effects. 1. Still a further feature of my improved stencil residesin the fact that the stencil duringmanw facture, developing and fixing,is not subjected to 5 temperatures which cause expansion and comtraction thereof.

Still a further feature of the invention resides in a novel constructionwhereby the stencil may be used to take an impression either by a photo-19 graphic process or by direct printing contact.

Other features of the invention will appear as I the nature thereof isunderstood for which purpose reference will be had to the followingspecification and the accompanying drawing. 15

In the drawing; I Figure l is a perspective view of a completed stencilconstructed in accordance with the present invention,

Figures 2, 3 and ii illustrate one manner in 20 which my improvedstencils may be formed, and v Figure 5 is a perspective longitudinalsectional view illustrating a finished stencil blank before it has beensensitized.

indicated by the reference character In and in Figure 2 the strip ofcardboard by which the base material is manipulated is designated I I.

The reference numeral "designates a suitable receptacle preferably inthe form of a relatively '40 shallow tray such as used for containingvarious solutions in the photographic art and it is this type ofreceptacle which Iprefer to use in carrying out my improved method orprocess.

After the strip 'of base material has been at- 45 tached to themanipulating strip of cardboard, the same is treated by floating it uponthe surface of a suitable solution which prepares the base material fortaking a sensitizing solution to be subsequently applied thereto. Thisstep of the 50 process is illustrated in Figure 2 of the drawing.

The solution with which the base material I0 is impregnated .by theforegoing step is designated ii in Figure 2 of the drawing and one'example of such a solution which I have successfully employed in themanufacture of stencils is as follows:

Egg albumin (dry flakes) 2 ounces Gum arabic in tears 2 ounces orn syrupor glycerol 1 ounce Sodium chloride 1 percent Sodium borate 5 percentChloride of lime percent alcohol in order to impart to the base materialthe desired color or tint.

The special ,pieces of base material which form the stencils are treatedas heretofore described with said compound, after which they are allowedto dry. Since the compound or emulsion with which they are treated is acold liquid the base material is not subjected to expansion orcontraction due to changes in temperature during either the impregnatingor drying steps.

After the stencils have been thus far completed they are stripped fromthe manipulating cardboard strip and attached to the regular perforatedstrip of cardboard material, which strip adapts them for use inconnectionwith duplicating machines, except that it is provided with arelatively stifi backing it formed with a dark or black field or areal'l which prevents deflection of light thus eliminating fog or halation,more especially when the impression is made by the photographic process.This is accomplished by gluing or otherwise fastening the stencils tothe strips. In Figures 3 and 4 this strip is designated l5 and isprinted with suitable instructions for use in the ordinary manner.

The stencils as now described are packed and are ready for sale to theultimate consumer. In this form the stencils will keep indefinitelywithout deterioration and they will not be affected in this condition bychanges in temperature, atmospheric or other conditions.

As far as described, however, the stencils have not been sensitized foruse and in accordance with the present invention this step is performedby the consumer. In order that the consumer may effectively produce thisstep he is provided with a sensitizing solution which he may apply tothe stencils in a manner to be now described.

This step is illustrated in Figures 3 and 4, which figures disclose areceptacle 20 similar to the receptacle l2 heretofore mentioned in whichthe sensitizing solution 2| is placed. The sensitizing solution beingplaced in the receptacle the stencil is grasped as illustrated inFigures 3 and 4 by the strip which forms its attachment to theduplicating machine and is floated over the sensitizing solution untilone surface thereof is covered with said solution. This is allowed todry in a modified light (not necessarily in a totally dark room) afterwhich the stencil is ready for exposure, which may be accomplishedeither by a photographic process or by direct printing contact with theto be impressed upon the stencil.

In sensitizing the stencils to take the impression I have found thatbest results are obtained with different solutions, the choice of whichis determined by the type of exposure to be employed in the making ofthe impression. For example, when the impression is to be made by directprinting contact the stencil is sensitized with a composition of onecharacter and when the impression is to be made by a photographic PartDistilled water 1 Acetone... 1 Ethyl alcohol 1 Glycerine Such asensitizing solution is not sensitive to light in its wet state andtherefore sensitizing, exposing and developing can be handled in daylight although it is not advisable to subject such a sensitized stencilto direct rays of light.

In making the impression by direct printing contact I prefer to employ acarbon lamp as a source of light and by placing the stencil into directcontact with the. material to be reproduced thereon and'in this positionsubjecting it to the action of the rays of a carbon lamp, an impressionupon the stencil will be had/ While I have stated that I prefer to use acarbon lamp such a light source is not essential and an impression maybe obtained upon the stencil by subjecting the assembled apparatus tothe action of natural light.

After the exposure is complete whether it is by artificial or naturallight, the stencil can be Nitrate of silver recrystalized 560 grainsGlacial acetic acid 2 fluid ounces Distilled water 10 fluid ouncesBefore applying the sensitive solution just mentioned it is necessary tosalt the base material by floating it in the following salting solutionand drying the same before subjecting it to the sensitizing solution:

Cadmium bromide 25 grains Potassium bromide 50 grains Potassium iodidegrains 5 percent albuminized distilled water l0 fluid ounces After thebase material has been subjected to this salting solution it is floatedon the sensitiz-' 1 ing solution and is then ready for exposure in acamera or similar photographic device in order that the photographicimpression may be had.

After the photographic exposure the stencil is immersed in the followingsolution for catalyzing:

Ounces Ammonium bichromate c. p l Sulphuric acid ,5 Water 70 following:

. Ounces Sodium hyposulphite 6 Formalin 2 Water 70 in which bath it isleft for a period of approximately three minutes after which it isthoroughly washed in cold water and dried, after which it is ready foruse in the ordinary manner.

From the foregoing it will be apparent that the present inventionprovides a sensitive stencil which in its original state, however, isnot of the sensitive type but is rendered sensitive by the consumerthrough the medium of certain solutions which are furnished to theconsumer.

Inasmuch as the several solutions employed are all employed in the coldstate the resulting stencils will be of uniform character since allexpansion and contraction of the base material is eliminated. This isimportant since it permits of the use of a number of stencils for theproduction of multicolored work all of which stencils will register andproduce multicolored work of a very high quality.

While I have stressed the fact that the stencils are preferablysensitized by the user, I wish it understood that stencils forphotographic purposes may be manufactured for sale already sensitizedwith the salting solution and silver nitrate mixed in the coatingemulsion and as thus made, offered for sale.

Having thus described the invention, what is claimed as new and what itis desired to secure by Letters Patent oi the United States, is:

1. The method of making duplicating stencils which comprisesimpregnating a sheet of fibrous base material with a cold protective andpresensitizing emulsion, drying the sheet, and subsequently subjectingthe sheet to a cold sensitizing bath, the sheet during said steps beingsubjected to a uniform temperature, and said first mentioned stepimmunizing the sheet against expansion or contraction due to changes intemperature or other atmospheric conditions during the intervaloccurring before the subsequent steps.

2. The method of making duplicating stencils which comprisesimpregnating a sheet of fibrous base material with a cold protective andpresensitizing emulsion and drying the sheet at a uniform temperature torender the sheet immune from. expansion or contraction when subjecte toatmospheric or temperature changes durin the interval occurring beforesubsequent treatment of the sheet, providing a backing for the sheethaving a darkened area over its major portion, immersing the sheet in acold sensitizing bath to prevent physical changes of the sheet andfinally removing the backing sheet without injury to the sensitizedsurface of the sheet.

ALBERTO MARIO GOMES.

